Roslund, L.K. Al-Najdawi, M.A. Balbin, L.F. Benedictsson, S.M. Ebbeni, M. Holz, M. Tarawneh, H. Åhnberg, K. JACoW Publishing Geneva, Switzerland 2673-5520 978-3-95450-250-9 10.18429/JACoW-MEDSI2023-THPPP049 English 346-348 undulator MMI FEL laser GUI Contribution to a conference proceedings 2024 2024-07 https://doi.org/10.18429/JACoW-MEDSI2023-THPPP049 https://jacow.org/medsi2023/papers/thppp049.pdf The APPLE X is a compact elliptically polarizing undulator with a small round magnetic gap that provides full polarization control of synchrotron radiation at a lower cost and in less built-in space than comparable devices. The APPLE X will be the source for MAX IV’s potential future Soft X-ray (SXL) FEL. The mechanical design, finite element analysis optimization, assembly process, magnetic measurements, and shimming of a full-scale 2 m, 40 mm-period SmCo permanent magnet undulator are presented.